### Biological Basis of the Code The provided code snippet is part of a computational model designed to simulate synaptic transmission in neural cells, focusing on the conductance of AMPA and NMDA receptors, two key components of excitatory synaptic transmission in the brain. #### AMPA and NMDA Receptors AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) and NMDA (N-methyl-D-aspartate) receptors are subtypes of glutamate receptors that mediate fast synaptic transmission in the central nervous system. They play crucial roles in synaptic plasticity, learning, and memory. Here's how the code captures their biological functions: - **AMPA Receptors**: These receptors mediate most of the fast excitatory synaptic transmission in the brain. When activated by glutamate, they allow the flow of Na⁺ (and to a lesser extent Ca²⁺) ions into the postsynaptic neuron, resulting in a rapid depolarization known as an excitatory postsynaptic potential (EPSP). - **NMDA Receptors**: Unlike AMPA receptors, NMDA receptors are both voltage-dependent and ligand-gated. In addition to binding glutamate, they require postsynaptic depolarization to remove a Mg²⁺ block from the channel. Once activated, NMDA receptors allow the flow of Ca²⁺ and Na⁺ ions, contributing to synaptic plasticity mechanisms such as long-term potentiation (LTP). #### Objective of the Code The objective of the code is to adjust the synaptic conductance values of AMPA and NMDA receptors such that a single pulse stimulus induces a 5mV depolarization at every synapse along a modeled neuron. This is a common task in computational neuroscience aimed at calibrating the model to reflect physiological conditions. - **Conductance Calibration**: The code iteratively tunes the `GMAX` parameter, which represents the maximum synaptic conductance, to achieve the desired depolarization. This process attempts to ensure that the simulated synaptic response (EPSP) matches experimental observations of synaptic dynamics. - **Specific Goals**: The code considers the mixed involvement of AMPA and NMDA receptors in generating the EPSP by incorporating a predefined AMPA to NMDA conductance ratio (`NMDA_AMPA_RATIO`), which reflects their relative contributions to synaptic transmission. #### Biological Relevance The tuning of synaptic conductances is crucial for accurately simulating neural responses to synaptic inputs, which is essential for understanding neural network dynamics and their capabilities for processing information, storing memories, and adapting through synaptic plasticity. The model's ability to replicate realistic synaptic behavior helps in exploring various hypotheses about neuronal computation and neurophysiological phenomena.